Aiyoh normal je tu! A few of us mums had the same confusion, ultrasound dating is usually more accurate than apps, so ikut je apa kata doktor your scan lah, especially if it's from early pregnancy scan. Apps calculate based on LMP je which boleh off by a week or two, but ultrasound measurement tengok actual baby size so it's more reliable, best thing is tanya your doc which dating he's going with for your EDD and follow that je, will make things clearer later!